1500 watt heater. Enough?

[TNGW1500SE]

I'm thinking of installing a 1500 watt, 120 volt, electric, wall mount heater in my 30 foot, 30 amp, class A. I know this thing isn't going to keep us warm when it's 20 degrees out but do you think it would be enough on those chilly nights when it gets down to 45? I have a place to mount it that's deep enough and out of the way. I'd "share" the A/C 20 amp breaker between the A/C and this heater. Only one would ever be on at a time and I'd run 12/2, with ground, hard wired, from the breaker to the heater. We have a little tabletop heater now that does "ok" but we have to store it away when not in use and when it's "in use" it's on the table. Looks like this one would draw about 12.5 amps and heat with 5000 or so BTU.

[rhagfo]

ctilsie242 wrote:
I would look for a "cheap heat" system, which would let you run your RV furnace, but with an electric element, rather than LP gas. This will get the warm air not just circulating around, but in the basement as well.

My order of preference: RV furnace, a Vornado electric heater, a Mr. Buddy heater. The RV furnace is the safest and heats my rig the quickest with zero added humidity. The electric heater also doesn't add humidity, but doesn't heat that much, especially a medium-size, poorly insulated rig like my TT. The Mr. Buddy heater with ventilation does surprisingly well, provides you leave the top window open, and have another window open for incoming air. However, the Mr. Buddy isn't as safe or foolproof as the other ways, so I leave it for last.

While the initial cost is not cheap, we have been using the Cheap Heat system for close to a year and it works great. We have two Beagles and portable heaters would be a concern. In addition DD was a Firefighter and saw way too many fires caused by portable electric heaters. Most outlets in RVs are on 15 amp circuits on 14 gauge wire, not great for continuous use.

[Rice]

TNGW1500SE wrote:
My RV is in the garage all winter. We are going to Maggie Valley May thru Oct. We'll only use it those months. I just need to knock the chill off at night.

I have the heater you mentioned in your first post. I love it because you don't have to have it sitting out in the open when you're using it and you don't have to store it--it just sits on the wall.

The last time I tested it, it was using 11 amps--all of my electric heaters lose oomph over time, and I replaced the guts of this one a few years ago because I thought its heating capability had dropped.

It's the heater we use the most in our 40-foot relatively well-insulated motorhome. It's installed at the entrance to the bedroom, and keeps the coach comfortable when the temperature drops into the 40s overnight.

[austinjenna]

I guess my approach is more simplistic. I just have 2 1500 watt heaters that I bring out when I need too, one points towards the back and one towards the front and I set the furnace on as a backup although that has never come on.

I don't camp in the winter so for fall cold weather it has worked fine for me.

[TNGW1500SE]

Johno02 wrote:
Considering the last few winters in Tennessee, the answer is NO. We spent this winter in our small class A, and ran two 1500+W portables most of the time, and still had to use propane some nights. One portable works pretty good down to about 40 or so, but a good down comforter on the bed with a foam mattress was essential. We are 50A, so we have two good 110v circuits to run heaters on, one on each side of the rig.

My RV is in the garage all winter. We are going to Maggie Valley May thru Oct. We'll only use it those months. I just need to knock the chill off at night.

[Johno02]

Considering the last few winters in Tennessee, the answer is NO. We spent this winter in our small class A, and ran two 1500+W portables most of the time, and still had to use propane some nights. One portable works pretty good down to about 40 or so, but a good down comforter on the bed with a foam mattress was essential. We are 50A, so we have two good 110v circuits to run heaters on, one on each side of the rig.

[theoldwizard1]

For a 30' coach, I would want 2 heaters, even if it is just for better distribution. This will be under your 30A limit, but if you want to make coffee or run the microwave, you may have to turn one off !

[ctilsie242]

I would look for a "cheap heat" system, which would let you run your RV furnace, but with an electric element, rather than LP gas. This will get the warm air not just circulating around, but in the basement as well.

My order of preference: RV furnace, a Vornado electric heater, a Mr. Buddy heater. The RV furnace is the safest and heats my rig the quickest with zero added humidity. The electric heater also doesn't add humidity, but doesn't heat that much, especially a medium-size, poorly insulated rig like my TT. The Mr. Buddy heater with ventilation does surprisingly well, provides you leave the top window open, and have another window open for incoming air. However, the Mr. Buddy isn't as safe or foolproof as the other ways, so I leave it for last.

[dewey02]

Yikes - this thread has so many misconceptions about what heating does to moisture. Fortunately, some other posters have tried to correct these misconceptions.

If you have a ventless propane heater (like a Mr. Buddy) then yes...it will add moisture to the air as the propane burns. But having an electric heater or your factory installed propane heater going won't add moisture to your trailer. As was said, the trailer's propane heater vents to the outside, so that is where the moisture generated by burning propane goes. The electric heater burns no hydrocarbons and therefore contributes no moisture.

The vast majority of moisture in your trailer comes from your own body, respiration mostly, but also via your pores. And then there is showering, dishwashing, cooking, etc. Heating hot water via your gas water heater doesn't contribute moisture directly because it (like your furnace) is vented to the outside. You only notice the increased moisture when it is colder because at lower temperatures, surfaces like your windows and walls behind closed closet doors are cold so the moisture condenses on them.

Propane combustion equation: C3H8 + 5O2 = 3CO2 + 4H2O (Propane + Oxygen = Carbon Dioxide and Water) Of course, incomplete combustion can also result in CO (Carbon monoxide).

Relative Humidity: The relative humidity is the amount of water vapor the air is holding right now as a percentage of what it would be holding if it were saturated. ... If you increase the temperature, however, the amount of water vapor the air can hold increases, so the relative humidity decreases.

[DrewE]

myredracer wrote:

There is a tremendous amount of moisture released into the interior air from human bodies, cooking, showering and from pets. One human body alone on average release 5 cups per day into the air. No difference with electric heat or a furnace, there's a LOT of moisture that needs to be expelled somehow. An electric heater doesn't remove moisture. Remember, the warmer the air is, the more moisture it will hold so as an electric heater warms the space, the higher the RH will be (unless moisture is getting exhausted out).

The relative humidity goes down at the temperature goes up, assuming the actual amount of moisture in the air remains the same, because the air can hold more moisture. The fixed amount of moisture is thus a lower percentage of the amount the air can hold before it starts condensing. Obviously things that add moisture to the air like cooking and showering and breathing and sweating do increase the relative humidity, assuming no change in the ambient temperature.

The main problem in the winter is the lack of air exchange, which means the moisture builds up in a small space (like an RV). With a larger space like many houses, the problem is the opposite; there's sufficient air exchange that heating the replacement air causes a low relative humidity, and normal activities don't generate enough moisture to raise it to a reasonable level, so some form of additional humidification is helpful.

[myredracer]

spoon059 wrote:

myredracer wrote:
In colder weather, you need to ventilate the interior to remove moisture laden air. If you don't, you can end with issues like mold, rot and delamination. An electric dehumidifier may be needed if you plan to use your camper often in cold weather. Cracking vents and windows and/or running a fan means you lose some heat. Don't seal everything up with in an effort to retain heat.

Very true of the propane furnace, which can put out a lot of moisture. An electric space heater will actually dry out the area, not introduce more humidity.

How does a furnace release moisture inside? The combustion exhaust and intake are vented directly to the exterior.

There is a tremendous amount of moisture released into the interior air from human bodies, cooking, showering and from pets. One human body alone on average release 5 cups per day into the air. No difference with electric heat or a furnace, there's a LOT of moisture that needs to be expelled somehow. An electric heater doesn't remove moisture. Remember, the warmer the air is, the more moisture it will hold so as an electric heater warms the space, the higher the RH will be (unless moisture is getting exhausted out).

[spoon059]

myredracer wrote:
In colder weather, you need to ventilate the interior to remove moisture laden air. If you don't, you can end with issues like mold, rot and delamination. An electric dehumidifier may be needed if you plan to use your camper often in cold weather. Cracking vents and windows and/or running a fan means you lose some heat. Don't seal everything up with in an effort to retain heat.

Very true of the propane furnace, which can put out a lot of moisture. An electric space heater will actually dry out the area, not introduce more humidity.

[myredracer]

Chris Bryant wrote:

afidel wrote:

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

1800W is correct for a heater as it falls under continuous load so the circuit needs to be derated by 20%.

I thought 1920 was 20% down- 20 amps times 120 volts equals 2400 watts, less 480 watts (20% of 2400) equals 1920 watts.
Or is there an additional derating due to constant load? My NEC is still packed 🙂

Interestingly, in Canada we can run wire on fixed space heaters at 100% of it's rating while breakers must be derated to 80%. Heaters are considered non-continuous loads in buildings. Nothing burns up here, including our house which is part electric heat. AFAIK, the NEC still considers heaters to be continuous and requires derating of wire and breakers by 80% for fixed space heating. Fixed heaters in an RV are going to be a different thing because they won't cycle on/off like in a building (which will have good insulation and properly sized heaters) and I would def. not exceed 1440 watts on 15 amp wire and breaker or 1920 watts on 20 amp wire and breaker. Plug-in portable heaters are a different matter and can be rated at 1500 watts and have 16 ga. cord wire and be plugged into a 15 amp recept.

[myredracer]

You don't say what you have which may or may not make a difference. I installed recessed heaters in our TT and can add some comments.

It depends somewhat on how well your camper is insulated. Many are not plus they can leak like a sieve. We had lots of holes in the floor in ours, including one about 8x8" and I sealed them all up with foam. Having run lots of various wiring through the ceiling, I've found the insulation workmanship in the ceiling cavity to be terrible and in some locations there isn't any.

Your floor will feel uncomfortably cold in colder temps. You may want to wear thicker socks. If you have an enclosed underbelly, tanks and piping won't get any heat so if the temps. will drop below 32, something could freeze up.

You will need to maintain the required safety clearances on all sides of the heater. Can be a challenge to find a suitable spot. I installed a semi-recessed heater on the ceiling in a previous TT because there was no other place - worked fine.

In colder weather, you need to ventilate the interior to remove moisture laden air. If you don't, you can end with issues like mold, rot and delamination. An electric dehumidifier may be needed if you plan to use your camper often in cold weather. Cracking vents and windows and/or running a fan means you lose some heat. Don't seal everything up with in an effort to retain heat.

I'd get a heater with a squirrel cage blower instead of a propeller fan because they're much quieter. These heaters aren't cheap and don't get the cheapest one you can find. You don't need to share the circuit for the AC unit, Just get tandem breaker and run a new circuit back to the panel. You'll never run the heaters and AC together (and if you did, you'll just trip a breaker). Wiring can be run 100% concealed via ceilings, interior walls, cabinetry, under shower, etc. It will take longer to get the interior up to a comfortable temp. when you get to a new site but can always use the furnace at first. I'm an EE and have never run into a heater that doesn't put out it's rated wattage and they must meet a UL standard that specifies output requirement. Note that ratings are at 120 volts and heat output varies as the square of the voltage so try and have good voltage. If you can, install a wall mounted t'stat because they function better compared to an integral built-in one on a heater. I'd suggest two smaller wattage heaters in different areas for more even heating.

We have a 29' TT and I installed two recessed heater like the OP shows plus a 1KW recessed kickspace heater below the stove and have it set up at 2,000 watts total. One heater is above the bed, one is in the bathroom and one is at the rear of the TT in the kitchen. Provides even and comfy heating from front to rear. I used King Pic-a-watt "PAW" heaters which have adjustable tap settings from 250 to 1500 watts in 250 watt increments. I made my own demand controller using a current sensing relay that automatically shuts off the heaters when something gets plugged in that exceeds 30 amps total into the TT. I used wall mounted low voltage thermostats for better control. 2,000 watts isn't quite enough below 40F as the heaters run continuously, esp. the one in the kitchen as it covers a larger area. I did this a few seasons ago and haven't had to use the furnace since - not sure if it still works, lol. And yes, these heaters put out their rated wattage.

[Chris_Bryant]

afidel wrote:

Chris Bryant wrote:
Fwiw, if you are hard wiring it, you can go up to 1800 watts on that 20 amp circuit.
Actually, I believe you can go even higher, like 1920 watts.

1800W is correct for a heater as it falls under continuous load so the circuit needs to be derated by 20%.

I thought 1920 was 20% down- 20 amps times 120 volts equals 2400 watts, less 480 watts (20% of 2400) equals 1920 watts.
Or is there an additional derating due to constant load? My NEC is still packed 🙂